Axolotl
* The Axolotl (Ambystoma mexicanum) is a neotenic salamander, closely related to the tiger salamander. Larvae of this species fail to undergo metamorphosis, so the adults remain aquatic and gilled. * The species originates from numerous lakes, such as Lake Xochimilco underlying Mexico City. * Axolotls are used extensively in scientific research due to their ability to regenerate limbs. * As of 2010, wild axolotls are near extinction due to urbanization in Mexico City and polluted waters. Non-native fish, such as African tilapia and Asian carp, have also recently been introduced to the waters. * These new fish have been eating the axolotls' young, as well as its primary source of food. * The axolotl is currently on the International Union for Conservation of Nature's annual Red List of threatened species. Description A sexually mature adult axolotl, at age 18–24 months, ranges in length from 15–45 cm (6–18 in), although a size close to 23 cm (9 in) is most common and greater than 30 cm (12 in) is rare. Axolotls possess features typical of salamander larvae, including external gills and a caudal fin extending from behind the head to the vent. Their heads are wide, and their eyes are lidless. Their limbs are underdeveloped and possess long, thin digits. Males are identified by their swollen cloacae lined with papillae, while females are noticeable for their wider bodies full of eggs. Three pairs of external gill stalks (rami) originate behind their heads and are used to move oxygenated water. The external gill rami are lined with filaments (fimbriae) to increase surface area for gas exchange. Four gill slits lined with gill rakers are hidden underneath the external gills. Axolotls have barely visible vestigial teeth, which would have developed during metamorphosis. The primary method of feeding is by suction, during which im gay rakers interlock to close the gill slits. External gills are used for respiration, although buccal pumping (gulping air from the surface) may also be used to provide oxygen to their lungs. Axolotls have four different colours, including two mutant colors. The two normal colors are "wildtype" (varying shades of brown usually with spots) and melanoid (black). The two mutant colors are leucistic (pale pink with black eyes) and albino (golden, tan or pale pink with pink eyes). Habitat and ecology The axolotl is only native to Lake Xochimilco and Lake Chalco in central Mexico. Unfortunately for the axolotl, Lake Chalco no longer exists, as it was artificially drained to avoid periodic flooding, and Lake Xochimilco remains a remnant of its former self, existing mainly as canals. The water temperature in Xochimilco rarely rises above 20 °C (68 °F), though it may fall to 6 to 7°C in the winter, and perhaps lower. The wild population has been put under heavy pressure by the growth of Mexico City. Axolotls are also sold as food in Mexican markets and were a staple in the Aztec diet. They are currently listed by CITES as an endangered species and by IUCN as critically endangered in the wild, with a decreasing population. Axolotls are members of the Ambystoma tigrinum (Tiger salamander) complex, along with all other Mexican species of Ambystoma. Their habitat is like that of most neotenic species—a high altitude body of water surrounded by a risky terrestrial environment. These conditions are thought to favor neoteny. However, a terrestrial population of Mexican Tiger Salamanders occupies and breeds in the axolotl's habitat. The axolotl is carnivorous, consuming small prey such as worms, insects, and small fish in the wild. Axolotls locate food by smell, and will "snap" at any potential meal, sucking the food into their stomachs with vacuum force. Category:Salamanders